The eradication of HIV and cure of infected patients has failed chiefly because HIV establishes a latent form of infection in resting CD4 memory T-cells. Although a total of only 106-107 latently infected ceils may be present in infected patients, the long lived nature of these cells (T1/2 of 44 months) predicts that -70 years of antiviral therapy will be required for ablation of this reservoir. A different strategy is clearly required to attack this clinical problem. One approach could involve purging of the virus from these cells by stimulating transcriptional activation of the HIV LTR. We hypothesize that the NF-_B/Rel family of transcription factors plays a pivotal role as physiological antagonists of HIV latency. We propose to conduct a comprehensive set of studies exploring the molecular basis for HIV latency and the role played by NF-_cB/Rel proteins. These studies will exploit a new cellular model of HIV latency, J-Lat cells, bona fide latently infected CD4 memory T ceils from infected patients, and a primate model of lentiviral latency. These studies will involve close and active collaborations with Dr. Eric Verdin (Project 1) Dr. Matija Peterlin (Project 3) and Drs. Tom North and Paul Luciw (Core B) which together comprise our PPG team. In Specific Aim 1, we will determine which members of the NF-KB/Rel family of transcription factors function as the most potent activators of latent HIV and will explore whether new insights into the regulation of NF-KB/Rel action can be exploited to reverse HIV latency. In Specific Aim 2, we will assess the molecular basis of viral latency using chromatin immunoprecipitation (CHIP) assays to identify cellular factors that bind to the HIV LTR KB enhancers under the opposing conditions of viral latency and active viral replication. In Specific Aim 3, we will focus on the intriguing interplay of NF-KB with PTEFb, the cellular enzyme complex hijacked by HIV Tat to promote high level viral gene expression. These studies will dissect the molecular basis for NF-KB assembly with PTEFb and explore whether the initial production of Tat depends on this action of NF-KB. In Specific Aim 4, we will advance our studies of HIV latency and its potential antagonism by NF-KB into an in vivo model system. We will investigate whether deletion of the _cB enhancers in the HIV LTR of SHIV viruses enhances latent infection of rhesus memory CD4 T-cells and conversely whether substitution of a constitutively active T cell enhancer impairs latency. Finally, we will explore whether agents known to activate and sustain nuclear NF-KB action (prostratin and phenylbutyrate) decrease the frequency of cells latently infected with these SHIVs. These studies promise to advance our understanding of the molecular, biochemical, and cellular basis for HIV latency, which in turn may lead to new rational approaches to solving this difficult clinical problem.